Following renaming of script.

Add script converting Graph-tool output to edgelist. So we can use
analysis scripts developed in Overlap on results of trajectory scripts.

Move tests on trajectories to new test file `Trajectories/tests.json`.

Directory Tests was created in commit 40a1c5aa.

Rewrite following an idea of R\'emi Laxenaire: loop on edges in order of
ascending cost function.

Rename trajectories to `traj_segm` and `expanded_trajectories` to
`expanded_traj`.

No need for this property to be internal.

Instead of a global variable with hidden modification in a method of Visitor.

So that segments in a trajectory are in chronological order.

This is a new reversion in a series of reversions. See commit
836392d7. The idea now is to allow us to run a single test in a series,
taking advantage of the archive option in recent versions of
`test_compare.py`.

We are in the else branch of `if src.out_degree() > 1` and src is the
source of an edge so `src.out_degree()` must be 1.

Correct name of property from `segment` to `inst_eddies`.

Correct name of property from `nl_cost_function` to `cost_function`.